National Business Park 302

Heating, Ventilating and Air Conditioning System

The National Business Park 302 (NBP 302) project involved construction of a 160,000 sq. ft., $1.6 million shell office structure which will be LEED® certified for Core and Shell. Whiting-Turner Contracting Company was the general contractor and Mechanical Engineering & Construction Corporation (MEC²) was the mechanical contractor responsible for the heating, ventilating, air conditioning, and plumbing system installation.

Construction was an intense coordination process with the Owner, COPT, the commissioning agent, general contractor and the sub-contractors to build an office building that maintained site cleanliness, safety and environmentally friendly impacts to the existing area.

The HVAC system serving NBP 302 consists of vertical self-contained, water-cooled air conditioning with variable air volume units distributing supply air to fan-powered boxes with electric reheat systems. The core of the building contains elevator lobbies and restrooms; this portion of the building was finished.

The office portion of the building was equipped with fan-powered boxes with controls and no low-pressure ductwork or air devices. The building is equipped with roof-mounted, energy-recovery units that supply ventilation outside air to the vertical self-contained supply units.

Two roof-mounted cooling towers reject heat for 200 tons of cooling each. The penthouse pump room consists of four base-mounted pumps and a flat plate heat exchanger that trades heat between the condenser water loop for the vertical self-contained HVAC unit and the cooling tower water loop.

The overall heating, ventilating and air conditioning system serving the building is monitored and controlled by a direct-digital computer-based control system. The control system automatically coordinates the function of all mechanical components to assure economical and reliable operation. The system may be monitored within the building and remotely for failures of equipment or operating criteria outside of pre-set levels.

We provided the underground plumbing utilities for sanitary, water, and storm water as well as providing the plumbing piping for stacked gang toilets for each tenant floor.

Challenges to this installation included a change in the design of the cooling tower elevation at the roof. The design team modified the height that the cooling tower was to project off the roof line. This caused operational and control issues. The 3-way control valve required modification and piping strategies were changed in the field to give the pumps the required pressure for optimal operation. Coordination between the design team and the construction team was critical for the quick diagnoses of the problem and the eventual resolution. By utilizing the talents of all involved in the building process, we averted a potentially large delay to the construction schedule.

LEED® requirements added additional tasks to the construction process that included keeping stored materials from making direct contact with the floor, temporary capping of ductwork and terminal units to minimize debris entrainment, providing required filtration over the return openings, and specific leakage testing of our systems.

Close coordination with all trades was critical to minimize dust and debris in construction practices, reviewing the building construction to verify acceptable sealing of windows and walls, and proper installation of building insulation. The building is currently occupied and performing with the intended results.